An electrochemical approach is presented for carrying out controlled modification of carbon and metal surfaces with aryl groups through mild anodic oxidation of arylhydrazines. Electrochemical, PM-IRRAS, and ellipsometrical measurements reveal that monolayers are formed, the thickness of which is essentially independent of the substituent, pH, and grafting time and potential. This feature makes the approach very tolerant toward variations in the experimental conditions. Hence, this method should be considered as a strong option if the aim is to form thin, well-defined, and covalently assembled aryl layers on surfaces.